CVE-2026-9679

MEDIUMPre-NVD 5.95.9—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 83% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
5.9
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.9Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Impact: undici's cookie parser in parseSetCookie percent-decodes cookie values via qsUnescape, turning encoded sequences like %0D%0A, %00, %3B, and %3D into their literal byte equivalents. RFC 6265 §5.4 does not specify any decoding and browsers do not decode either.

Applications that parse a Set-Cookie header and then forward the parsed value into a response header (proxies, middleware, SSR frameworks) become vulnerable to HTTP response header injection: an attacker-controlled upstream can inject arbitrary Set-Cookie, Location, or Cache-Control headers into the application's downstream response, enabling session fixation, open redirect, or cache poisoning.

Affected applications are those that use undici's cookie parsing (parseSetCookie, parseCookie, getSetCookies) and forward the parsed cookie value into a response header.

This was introduced in undici 7.0.0 via PR #3789.

Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0.

Workarounds: If upgrade is not immediately possible, do not forward values returned by parseSetCookie/parseCookie/getSetCookies directly into response headers; sanitize the value first to strip or reject CR, LF, NUL, ;, and = bytes.

CVSS v3
5.9
EG Score
5.9(medium)
EPSS
17.1%
KEV
Not listed

Published

June 17, 2026

Last Modified

June 25, 2026

Advisory Details (2)

Auto-updated Jun 17, 2026
Patch available. Sources: github.
github Patch Available

undici vulnerable to HTTP header injection via Set-Cookie percent-decoding · Advisory · nodejs/undici · GitHub

https://github.com/nodejs/undici/security/advisories/GHSA-p88m-4jfj-68fv
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html

Vendor Advisories for CVE-2026-9679(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
undici—8.5.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 40× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-07 05:44 UTCEG score recompute
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 06:28 UTCEG score recompute
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-05 07:15 UTCEG score recompute
  6. 2026-07-05 02:31 UTCEPSS rescore
  7. 2026-07-04 07:55 UTCEG score recompute
  8. 2026-07-04 06:31 UTCEPSS rescore
  9. 2026-07-03 07:12 UTCEG score recompute
  10. 2026-07-02 08:00 UTCEG score recompute
  11. 2026-07-01 15:07 UTCEPSS rescore
  12. 2026-07-01 08:48 UTCEG score recompute
  13. 2026-06-30 23:22 UTCEPSS rescore
  14. 2026-06-30 09:37 UTCEG score recompute
  15. 2026-06-29 14:06 UTCEPSS rescore
  16. 2026-06-29 10:25 UTCEG score recompute
  17. 2026-06-28 14:07 UTCEPSS rescore
  18. 2026-06-28 11:10 UTCEG score recompute
  19. 2026-06-28 04:56 UTCEPSS rescore
  20. 2026-06-27 11:58 UTCEG score recompute
  21. 2026-06-27 03:08 UTCEPSS rescore
  22. 2026-06-26 12:47 UTCEG score recompute
  23. 2026-06-25 13:50 UTCEPSS rescore
  24. 2026-06-25 13:36 UTCEG score recompute
  25. 2026-06-24 14:25 UTCEG score recompute
Show 15 more
  1. 2026-06-24 14:05 UTCEPSS rescore
  2. 2026-06-23 21:33 UTCEPSS rescore
  3. 2026-06-23 15:13 UTCEG score recompute
  4. 2026-06-22 15:58 UTCEG score recompute
  5. 2026-06-22 14:25 UTCEPSS rescore
  6. 2026-06-21 16:42 UTCEG score recompute
  7. 2026-06-21 14:56 UTCEPSS rescore
  8. 2026-06-21 01:59 UTCEPSS rescore
  9. 2026-06-20 17:31 UTCEG score recompute
  10. 2026-06-19 19:26 UTCEPSS rescore
  11. 2026-06-19 18:17 UTCEG score recompute
  12. 2026-06-18 19:03 UTCEG score recompute
  13. 2026-06-18 17:52 UTCEPSS rescore
  14. 2026-06-17 19:51 UTCEG score recompute
  15. 2026-06-17 19:50 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-9679?
CVE-2026-9679 is a medium vulnerability published on June 17, 2026. Impact: undici's cookie parser in parseSetCookie percent-decodes cookie values via qsUnescape, turning encoded sequences like %0D%0A, %00, %3B, and %3D into their literal byte equivalents. RFC 6265 §5.4 does not specify any decoding and browsers do not decode either. Applications that parse a…
When was CVE-2026-9679 disclosed?
CVE-2026-9679 was first published in the National Vulnerability Database on June 17, 2026, with the most recent update on June 25, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-9679 actively exploited?
CVE-2026-9679 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 17.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-9679?
CVE-2026-9679 has a CVSS v3 base score of 5.9 (NVD).
How do I remediate CVE-2026-9679?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-9679, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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