CVE-2026-19879

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreMEDIUM 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 — 3 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(medium)
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.

Affected Packages

(1 across 1 ecosystem)
Debian:14(1)
PackageVulnerable rangeFixed inDependents
undertow1.3.11-1 ... 2.3.8-2 (56 versions)——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 18× in last 7d / 79× 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. 2026-09-18 23:08 UTCEG score recompute
  2. 2026-09-18 23:08 UTCGHSA enrichment
  3. 2026-09-18 19:27 UTCEPSS rescore
  4. 2026-09-18 00:23 UTCEG score recompute
  5. 2026-09-18 00:23 UTCGHSA enrichment
  6. 2026-09-16 23:49 UTCEG score recompute
  7. 2026-09-16 23:49 UTCGHSA enrichment
  8. 2026-09-16 14:07 UTCEPSS rescore
  9. 2026-09-16 05:14 UTCEPSS rescore
  10. 2026-09-15 21:52 UTCEG score recompute
  11. 2026-09-15 21:51 UTCGHSA enrichment
  12. 2026-09-14 21:41 UTCGHSA enrichment
  13. 2026-09-13 22:32 UTCEG score recompute
  14. 2026-09-13 22:32 UTCGHSA enrichment
  15. 2026-09-13 16:46 UTCEPSS rescore
  16. 2026-09-12 23:48 UTCEG score recompute
  17. 2026-09-12 23:48 UTCGHSA enrichment
  18. 2026-09-12 15:00 UTCEPSS rescore
  19. 2026-09-12 01:03 UTCEG score recompute
  20. 2026-09-12 01:03 UTCGHSA enrichment
  21. 2026-09-11 14:52 UTCEPSS rescore
  22. 2026-09-11 09:36 UTCEPSS rescore
  23. 2026-09-11 02:18 UTCEG score recompute
  24. 2026-09-11 02:18 UTCGHSA enrichment
  25. 2026-09-10 09:34 UTCEPSS rescore
Show 73 more
  1. 2026-09-10 03:34 UTCGHSA enrichment
  2. 2026-09-09 04:50 UTCEG score recompute
  3. 2026-09-09 04:50 UTCGHSA enrichment
  4. 2026-09-08 22:00 UTCEPSS rescore
  5. 2026-09-07 20:44 UTCEG score recompute
  6. 2026-09-07 20:44 UTCGHSA enrichment
  7. 2026-09-07 16:01 UTCEPSS rescore
  8. 2026-09-06 21:56 UTCEG score recompute
  9. 2026-09-06 21:56 UTCGHSA enrichment
  10. 2026-09-06 13:47 UTCEPSS rescore
  11. 2026-09-05 23:11 UTCEG score recompute
  12. 2026-09-05 23:10 UTCGHSA enrichment
  13. 2026-09-05 00:27 UTCEG score recompute
  14. 2026-09-05 00:26 UTCGHSA enrichment
  15. 2026-09-04 05:06 UTCEPSS rescore
  16. 2026-09-04 01:00 UTCGHSA enrichment
  17. 2026-09-03 00:57 UTCEG score recompute
  18. 2026-09-03 00:57 UTCGHSA enrichment
  19. 2026-09-02 14:11 UTCEPSS rescore
  20. 2026-09-02 01:59 UTCEG score recompute
  21. 2026-09-02 01:59 UTCGHSA enrichment
  22. 2026-09-01 13:53 UTCEPSS rescore
  23. 2026-09-01 04:39 UTCEPSS rescore
  24. 2026-09-01 03:14 UTCGHSA enrichment
  25. 2026-08-31 04:24 UTCEG score recompute
  26. 2026-08-31 04:24 UTCGHSA enrichment
  27. 2026-08-30 19:17 UTCEPSS rescore
  28. 2026-08-30 05:39 UTCEG score recompute
  29. 2026-08-30 05:39 UTCGHSA enrichment
  30. 2026-08-30 01:22 UTCEPSS rescore
  31. 2026-08-29 06:55 UTCEG score recompute
  32. 2026-08-29 06:55 UTCGHSA enrichment
  33. 2026-08-28 21:41 UTCEPSS rescore
  34. 2026-08-28 02:25 UTCEG score recompute
  35. 2026-08-28 02:25 UTCGHSA enrichment
  36. 2026-08-27 14:25 UTCEPSS rescore
  37. 2026-08-27 03:40 UTCEG score recompute
  38. 2026-08-27 03:40 UTCGHSA enrichment
  39. 2026-08-26 14:46 UTCEPSS rescore
  40. 2026-08-26 04:56 UTCEG score recompute
  41. 2026-08-26 04:56 UTCGHSA enrichment
  42. 2026-08-25 13:48 UTCEPSS rescore
  43. 2026-08-25 06:13 UTCEG score recompute
  44. 2026-08-25 06:12 UTCGHSA enrichment
  45. 2026-08-24 07:29 UTCGHSA enrichment
  46. 2026-08-23 08:44 UTCGHSA enrichment
  47. 2026-08-22 10:00 UTCEG score recompute
  48. 2026-08-22 10:00 UTCGHSA enrichment
  49. 2026-08-21 23:49 UTCEPSS rescore
  50. 2026-08-21 11:16 UTCEG score recompute
  51. 2026-08-21 11:15 UTCGHSA enrichment
  52. 2026-08-20 22:55 UTCEPSS rescore
  53. 2026-08-20 12:26 UTCEG score recompute
  54. 2026-08-20 12:26 UTCGHSA enrichment
  55. 2026-08-19 17:03 UTCEPSS rescore
  56. 2026-08-19 13:42 UTCGHSA enrichment
  57. 2026-08-18 14:58 UTCEG score recompute
  58. 2026-08-18 14:58 UTCGHSA enrichment
  59. 2026-08-18 13:48 UTCEPSS rescore
  60. 2026-08-17 15:27 UTCEG score recompute
  61. 2026-08-17 15:27 UTCGHSA enrichment
  62. 2026-08-17 13:47 UTCEPSS rescore
  63. 2026-08-16 16:43 UTCEG score recompute
  64. 2026-08-16 16:43 UTCGHSA enrichment
  65. 2026-08-16 14:56 UTCEPSS rescore
  66. 2026-08-16 02:14 UTCEPSS rescore
  67. 2026-08-15 18:00 UTCGHSA enrichment
  68. 2026-08-14 19:16 UTCGHSA enrichment
  69. 2026-08-14 18:35 UTCEG score recompute
  70. 2026-08-14 18:35 UTCGHSA enrichment
  71. 2026-08-14 15:30 UTCEG score recompute
  72. 2026-08-14 14:59 UTCEG score recompute
  73. 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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