CVE-2026-39825

ReverseProxy forwards queries with more than urlmaxqueryparams parameters in net/http/httputil

ReverseProxy can forward queries containing parameters not visible to Rewrite functions. When used with a Rewrite function, or a Director function which parses query parameters, ReverseProxy sanitizes the forwarded request to remove query parameters which are not parsed by url.ParseQuery. ReverseProxy does not take ParseQuery's limit on the total number of query parameters (controlled by GODEBUG=urlmaxqueryparams=N) into account. This can permit ReverseProxy to forward a request containing a query parameter that is not visible to the Rewrite function. For example, the query "a1=x&a2=x&...&a10000=x&hidden=y" can forward the parameter "hidden=y" while hiding it from the proxy's Rewrite function.

CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Net/http Go

CVE-2026-39826

Escaper bypass leads to XSS in html/template

If a trusted template author were to write a <script> tag containing an empty 'type' attribute or a 'type' attribute with an ASCII whitespace, the execution of the template would incorrectly escape any data passed into the <script> block.

CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Html/template Go

CVE-2026-39819

Invoking "go bug" follows symlinks in predictable temporary filenames in cmd/go

The "go bug" command writes to two files with predictable names in the system temporary directory (for example, "/tmp"). An attacker with access to the temporary directory can create a symlink in one of these names, causing "go bug" to overwrite the target of the symlink.

CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed

Vendors

Golang Gotoolchain

Products

Go Cmd/go

CVE-2026-39817

Invoking "go tool pack" does not sanitize output paths in cmd/go

The "go tool pack" subcommand (usually used only by the compiler as an internal tool with known-good inputs) does not sanitize output filenames. Extracting a malicious archive file with the "pack" subcommand can write files to arbitrary locations on the filesystem.

CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed

Vendors

Golang Gotoolchain

Products

Go Cmd/go

CVE-2026-42501

Malicious module proxy can bypass checksum database in cmd/go

A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade your base Go toolchain. The go tool always validates the hash of a toolchain before executing it, so fixed versions will refuse to execute any cached, altered versions of the toolchain. The go tool trusts go.sum files to contain accurate hashes of the current module's dependencies. A malicious proxy exploiting this vulnerability to serve an altered module will have caused an incorrect hash to be recorded in the go.sum. Users who have configured a non-trusted GOPROXY can determine if they have been affected by running "rm go.sum ; go mod tidy ; go mod verify", which will revalidate all dependencies of the current module. The specific flaw in more detail: The go command consults the checksum database to validate downloaded modules, when a module is not listed in the go.sum file. It verifies that the module hash reported by the checksum database matches the hash of the downloaded module. If, however, the checksum database returns a successful response that contains no entry for the module, the go command incorrectly permitted validation to succeed. A module proxy may mirror or proxy the checksum database, in which case the go command will not connect to the checksum database directly. Checksums reported by the checksum database are cryptographically signed, so a malicious proxy cannot alter the reported checksum for a module. However, a proxy which returns an empty checksum response, or a checksum response for an unrelated module, could cause the go command to proceed as if a downloaded module has been validated.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Golang Gotoolchain

Products

Go Cmd/go

CVE-2026-39823

Bypass of meta content URL escaping causes XSS in html/template

CVE-2026-27142 fixed a vulnerability in which URLs were not correctly escaped inside of a <meta> tag's <content> attribute. If the URL content were to insert ASCII whitespaces around the '=' rune inside of the <content> attribute, the escaper would fail to similarly escape it, leading to XSS.

CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Html/template Go

CVE-2026-39836

Panic in Dial and LookupPort when handling NUL byte on Windows in net

The Dial and LookupPort functions panic on Windows when provided with an input containing a NUL (0).

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Net Go

CVE-2023-48795

ssh: Prefix truncation attack on Binary Packet Protocol (BPP)

The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message), and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled, aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP), implemented by these extensions, mishandles the handshake phase and mishandles use of sequence numbers. For example, there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API before 3.1.0-SNAPSHOT, Dropbear through 2022.83, Ssh before 5.1.1 in Erlang/OTP, PuTTY before 0.80, AsyncSSH before 2.14.2, golang.org/x/crypto before 0.17.0, libssh before 0.10.6, libssh2 through 1.11.0, Thorn Tech SFTP Gateway before 3.4.6, Tera Term before 5.1, Paramiko before 3.4.0, jsch before 0.2.15, SFTPGo before 2.5.6, Netgate pfSense Plus through 23.09.1, Netgate pfSense CE through 2.7.2, HPN-SSH through 18.2.0, ProFTPD before 1.3.8b (and before 1.3.9rc2), ORYX CycloneSSH before 2.3.4, NetSarang XShell 7 before Build 0144, CrushFTP before 10.6.0, ConnectBot SSH library before 2.2.22, Apache MINA sshd through 2.11.0, sshj through 0.37.0, TinySSH through 20230101, trilead-ssh2 6401, LANCOM LCOS and LANconfig, FileZilla before 3.66.4, Nova before 11.8, PKIX-SSH before 14.4, SecureCRT before 9.4.3, Transmit5 before 5.10.4, Win32-OpenSSH before 9.5.0.0p1-Beta, WinSCP before 6.2.2, Bitvise SSH Server before 9.32, Bitvise SSH Client before 9.33, KiTTY through 0.76.1.13, the net-ssh gem 7.2.0 for Ruby, the mscdex ssh2 module before 1.15.0 for Node.js, the thrussh library before 0.35.1 for Rust, and the Russh crate before 0.40.2 for Rust.

CVSS 3.1 · 5.9 Medium EPSS 93.5% KEV · Not listed

Vendors

9bis Apache Apple and 39 more

Products

Kitty Sshd Sshj and 74 more

CVE-2025-68121

Unexpected session resumption in crypto/tls

During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between the initial handshake and the resumed handshake, the resumed handshake may succeed when it should have failed. This may happen when a user calls Config.Clone and mutates the returned Config, or uses Config.GetConfigForClient. This can cause a client to resume a session with a server that it would not have resumed with during the initial handshake, or cause a server to resume a session with a client that it would not have resumed with during the initial handshake.

CVSS 3.1 · 9.1 Critical EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Crypto Tls Go

CVE-2026-33809

OOM from malicious IFD offset in golang.org/x/image/tiff

A maliciously crafted TIFF file can cause image decoding to attempt to allocate up 4GiB of memory, causing either excessive resource consumption or an out-of-memory error.

CVSS 3.1 · 5.3 Medium EPSS < 1% KEV · Not listed

Vendors

Golang

Products

Image Tiff

CVE-2026-27138

Panic in name constraint checking for malformed certificates in crypto/x509

Certificate verification can panic when a certificate in the chain has an empty DNS name and another certificate in the chain has excluded name constraints. This can crash programs that are either directly verifying X.509 certificate chains, or those that use TLS.

CVSS 3.1 · 5.9 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Crypto Tls Go

CVE-2026-27139

FileInfo can escape from a Root in os

On Unix platforms, when listing the contents of a directory using File.ReadDir or File.Readdir the returned FileInfo could reference a file outside of the Root in which the File was opened. The impact of this escape is limited to reading metadata provided by lstat from arbitrary locations on the filesystem without permitting reading or writing files outside the root.

CVSS 3.1 · 2.5 Low EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Os Go

CVE-2026-27142

URLs in meta content attribute actions are not escaped in html/template

Actions which insert URLs into the content attribute of HTML meta tags are not escaped. This can allow XSS if the meta tag also has an http-equiv attribute with the value "refresh". A new GODEBUG setting has been added, htmlmetacontenturlescape, which can be used to disable escaping URLs in actions in the meta content attribute which follow "url=" by setting htmlmetacontenturlescape=0.

CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Html/template Go

CVE-2026-27143

Missing bound checks can lead to memory corruption in safe Go in cmd/compile

Arithmetic over induction variables in loops were not correctly checked for underflow or overflow. As a result, the compiler would allow for invalid indexing to occur at runtime, potentially leading to memory corruption.

CVSS 3.1 · 9.8 Critical EPSS < 1% KEV · Not listed

Vendors

Golang Gotoolchain

Products

Go Cmd/compile

CVE-2026-27144

Miscompilation allows memory corruption via CONVNOP-wrapped array copy in cmd/compile

The compiler is meant to unwrap pointers which are the operands of a memory move; a no-op interface conversion prevented the compiler from making the correct determination about non-overlapping moves, potentially leading to memory corruption at runtime.

CVSS 3.1 · 7.1 High EPSS < 1% KEV · Not listed

Vendors

Golang Gotoolchain

Products

Go Cmd/compile

CVE-2026-32282

TOCTOU permits root escape on Linux via Root.Chmod in os in internal/syscall/unix

On Linux, if the target of Root.Chmod is replaced with a symlink while the chmod operation is in progress, Chmod can operate on the target of the symlink, even when the target lies outside the root. The Linux fchmodat syscall silently ignores the AT_SYMLINK_NOFOLLOW flag, which Root.Chmod uses to avoid symlink traversal. Root.Chmod checks its target before acting and returns an error if the target is a symlink lying outside the root, so the impact is limited to cases where the target is replaced with a symlink between the check and operation.

CVSS 3.1 · 6.4 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Internal/syscall/unix Go

CVE-2026-32281

Inefficient policy validation in crypto/x509

Validating certificate chains which use policies is unexpectedly inefficient when certificates in the chain contain a very large number of policy mappings, possibly causing denial of service. This only affects validation of otherwise trusted certificate chains, issued by a root CA in the VerifyOptions.Roots CertPool, or in the system certificate pool.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Crypto/x509 Go

CVE-2026-32288

Unbounded allocation for old GNU sparse in archive/tar

tar.Reader can allocate an unbounded amount of memory when reading a maliciously-crafted archive containing a large number of sparse regions encoded in the "old GNU sparse map" format.

CVSS 3.1 · 5.5 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Archive/tar Go

CVE-2026-32289

JsBraceDepth Context Tracking Bugs (XSS) in html/template

Context was not properly tracked across template branches for JS template literals, leading to possibly incorrect escaping of content when branches were used. Additionally template actions within JS template literals did not properly track the brace depth, leading to incorrect escaping being applied. These issues could cause actions within JS template literals to be incorrectly or improperly escaped, leading to XSS vulnerabilities.

CVSS 3.1 · 6.1 Medium EPSS < 1% KEV · Not listed

Vendors

Go Standard Library Golang

Products

Html/template Go

CVE-2025-47908

Denial of service via malicious preflight requests in github.com/rs/cors

Middleware causes a prohibitive amount of heap allocations when processing malicious preflight requests that include a Access-Control-Request-Headers (ACRH) header whose value contains many commas. This behavior can be abused by attackers to produce undue load on the middleware/server as an attempt to cause a denial of service.

CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed

Vendors

Golang

Products

Cors