CVE-2026-19879

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreHIGH confidence

Score 5.3 from GitHub Security Advisory published 2026-08-14. a secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this week
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.3Exploit: None knownExposed: 0

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

A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The writeString() method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific Unicode characters in user-controlled input that an application places into response headers. This can lead to the truncation of these characters into ASCII control characters or special symbols, potentially resulting in limited integrity impact or information disclosure if the application does not properly sanitize user input.

CVSS v3
5.3
EG Score
5.3(high)
EG Risk
28(Track)
EG Risk 28/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
15%
KEV
Not listed

Published

August 14, 2026

Last Modified

August 14, 2026

Advisory Details (2)

Auto-updated Aug 14, 2026
Patch available. Sources: redhat.
redhat

2516038 – (CVE-2026-19879) CVE-2026-19879 io.undertow/undertow: Undertow: HTTP response header integrity issue due to character truncation

https://bugzilla.redhat.com/show_bug.cgi?id=2516038
redhat Patch Available

CVE-2026-19879 - Red Hat Customer Portal

Affected: Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to a

https://access.redhat.com/security/cve/CVE-2026-19879

Vendor Advisories for CVE-2026-19879(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 22× in last 7d / 22× 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. 2026-08-20 22:55 UTCEPSS rescore
  2. 2026-08-20 12:26 UTCEG score recompute
  3. 2026-08-20 12:26 UTCGHSA enrichment
  4. 2026-08-19 17:03 UTCEPSS rescore
  5. 2026-08-19 13:42 UTCGHSA enrichment
  6. 2026-08-18 14:58 UTCEG score recompute
  7. 2026-08-18 14:58 UTCGHSA enrichment
  8. 2026-08-18 13:48 UTCEPSS rescore
  9. 2026-08-17 15:27 UTCEG score recompute
  10. 2026-08-17 15:27 UTCGHSA enrichment
  11. 2026-08-17 13:47 UTCEPSS rescore
  12. 2026-08-16 16:43 UTCEG score recompute
  13. 2026-08-16 16:43 UTCGHSA enrichment
  14. 2026-08-16 14:56 UTCEPSS rescore
  15. 2026-08-16 02:14 UTCEPSS rescore
  16. 2026-08-15 18:00 UTCGHSA enrichment
  17. 2026-08-14 19:16 UTCGHSA enrichment
  18. 2026-08-14 18:35 UTCEG score recompute
  19. 2026-08-14 18:35 UTCGHSA enrichment
  20. 2026-08-14 15:30 UTCEG score recompute
  21. 2026-08-14 14:59 UTCEG score recompute
  22. 2026-08-14 14:58 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-19879?
CVE-2026-19879 is a medium vulnerability published on August 14, 2026. A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The writeString() method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific…
When was CVE-2026-19879 disclosed?
CVE-2026-19879 was first published in the National Vulnerability Database on August 14, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-19879 actively exploited?
CVE-2026-19879 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 85.2% of all scored CVEs.
What is the CVSS score of CVE-2026-19879?
CVE-2026-19879 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2026-19879?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-19879, 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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