How severe is GHSA-8436-99hf-9mmv?

GHSA-8436-99hf-9mmv has a CVSS score of 3.7/10, rated LOW. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-8436-99hf-9mmv?

GHSA-8436-99hf-9mmv affects the following packages: undici (npm), undici (npm). Ecosystems affected: npm.

How do I fix GHSA-8436-99hf-9mmv?

Update undici to 7.29.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8436-99hf-9mmv is resolved across your whole dependency graph.

How do I detect GHSA-8436-99hf-9mmv in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undici, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-8436-99hf-9mmv if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-8436-99hf-9mmv actively exploited in the wild?

No public exploit code has been indexed for GHSA-8436-99hf-9mmv yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-8436-99hf-9mmv?

GHSA-8436-99hf-9mmv has an EPSS (Exploit Prediction Scoring System) score of 0.1%, placing it in the 2th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-8436-99hf-9mmv?

GHSA-8436-99hf-9mmv is classified as CWE-345 (CWE-345). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-8436-99hf-9mmv published, and has it been updated?

GHSA-8436-99hf-9mmv was published on September 29, 2026 and was last updated on September 29, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

LOW severity

undici vulnerable to caching and replay of unsafe HTTP method responsesGHSA-8436-99hf-9mmv

LOWFix: nodejs/undici@2be07bf

GHSA-8436-99hf-9mmv is a low-severity (CVSS 3.7) CWE-345 vulnerability in undici. A fix is available for undici — see the affected versions and patch details below.

Also known asCVE-2026-85008

Published

Sep 29, 2026

Updated

Sep 29, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-8436-99hf-9mmv.

EPSS Exploitation Probability

via FIRST.org ↗

0.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs2th percentile — riskier than 2% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-8436-99hf-9mmv by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,415 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

9Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

undicinpm

133.5Mdownloads / week

Description

Impact

undici's interceptors.cache() documents that it caches only safe HTTP methods. However, its internal skip-list is built by subtracting the configured methods from the safe-methods set, so an unsafe method (POST, PUT, PATCH, DELETE) never lands in the skip-list and is looked up against the cache store. Combined with the storage gate (canCacheResponse) having no method check, a heuristically-cacheable response (for example a 404) with an explicit Cache-Control: max-age=... to an unsafe method is stored and replayed on a subsequent identical request. The application's state-changing request never reaches the origin, and undici serves a fabricated response from the cache instead. This occurs with the default configuration (methods: ['GET']), which the public API does not allow widening to unsafe methods, so no application misuse is required; an untrusted origin can trigger it purely through its own response headers.

Patches

Upgrade to 7.29.1 or 8.10.2. The cache interceptor no longer reads from or writes to the cache for unsafe HTTP methods, while still invalidating existing cache entries on successful unsafe requests.

Workarounds

None.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`undici`	≥ 7.0.0&&< 7.29.1	7.29.1`npm install undici@7.29.1`
📦npm	`undici`	≥ 8.0.0&&< 8.10.2	8.10.2`npm install undici@8.10.2`

Affected Products

1 product · 2 configurations

Application

undicinodejs

≥ 8.0.0 && < 8.10.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undici, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update undici to 7.29.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8436-99hf-9mmv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatLow

This Low impact vulnerability in undici's cache interceptor can lead to integrity issues by caching responses for unsafe HTTP methods. Under certain default configurations, a malicious remote origin could cause stale or manipulated responses to be served from the cache, bypassing intended state changes. This risk is…

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

Source: Red Hat security advisory for GHSA-8436-99hf-9mmv (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Hardened Images	`nodejs26-main-11.19.0-1.26.7.0.1.5.2.hum1`	RHSA-2026:54389
Red Hat Hardened Images	`nodejs24-main-11.16.0-1.24.18.1.0.2.2.hum1`	RHSA-2026:54438
Red Hat Hardened Images	`grafana12-4-main-12.4.10-0.2.hum1`	RHSA-2026:66008

Frequently Asked Questions

### Impact undici's `interceptors.cache()` documents that it caches only safe HTTP methods. However, its internal skip-list is built by subtracting the configured methods from the safe-methods set, so an unsafe method (`POST`, `PUT`, `PATCH`, `DELETE`) never lands in the skip-list and is looked up against the cache store. Combined with the storage gate (`canCacheResponse`) having no method check, a heuristically-cacheable response (for example a `404`) with an explicit `Cache-Control: max-age=...` to an unsafe method is stored and replayed on a subsequent identical request. The application's