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: 0.4%CVSS: 5.3Exploit: None knownExposed services: Not assessed

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

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
5.3MEDIUMmedium confidence
EG Risk
29
EG Risk 29/100CISA SSVC

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%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
0.4%
EPSS %ILE
31st
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 14, 2026

Last Modified

August 14, 2026

Advisory Details (2)

Auto-updated Aug 14, 2026
No fix on record yet. 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
redhatMentions a patch (unverified)

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 rangeFix by version rangeDependents
undertow1.3.11-1 ... 2.3.8-2 (56 versions)
  • every version on: no fix on record
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 65× 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.

Showing the most recent 100 of 137 total refreshes for this CVE.

  1. 2026-10-09 20:06 UTCEPSS rescore
  2. 2026-10-08 17:11 UTCEPSS rescore
  3. 2026-10-07 23:47 UTCEPSS rescore
  4. 2026-10-07 08:07 UTCEG score recompute
  5. 2026-10-07 08:07 UTCGHSA enrichment
  6. 2026-10-06 15:17 UTCEPSS rescore
  7. 2026-10-06 09:22 UTCEG score recompute
  8. 2026-10-06 09:22 UTCGHSA enrichment
  9. 2026-10-05 17:42 UTCEPSS rescore
  10. 2026-10-04 23:21 UTCEPSS rescore
  11. 2026-10-04 22:13 UTCGHSA enrichment
  12. 2026-10-03 19:41 UTCEG score recompute
  13. 2026-10-03 19:41 UTCGHSA enrichment
  14. 2026-10-02 07:21 UTCEG score recompute
  15. 2026-10-02 07:21 UTCGHSA enrichment
  16. 2026-10-01 19:49 UTCEPSS rescore
  17. 2026-09-30 21:41 UTCEG score recompute
  18. 2026-09-30 21:41 UTCGHSA enrichment
  19. 2026-09-30 15:03 UTCEPSS rescore
  20. 2026-09-29 15:20 UTCEPSS rescore
  21. 2026-09-29 07:18 UTCEG score recompute
  22. 2026-09-29 07:18 UTCGHSA enrichment
  23. 2026-09-28 08:32 UTCEG score recompute
  24. 2026-09-28 08:32 UTCGHSA enrichment
  25. 2026-09-27 13:47 UTCEPSS rescore
Show 75 more
  1. 2026-09-27 09:37 UTCEG score recompute
  2. 2026-09-27 09:37 UTCGHSA enrichment
  3. 2026-09-26 15:58 UTCEPSS rescore
  4. 2026-09-25 03:23 UTCEG score recompute
  5. 2026-09-25 03:23 UTCGHSA enrichment
  6. 2026-09-23 20:46 UTCEG score recompute
  7. 2026-09-23 20:46 UTCGHSA enrichment
  8. 2026-09-22 20:56 UTCEG score recompute
  9. 2026-09-22 20:56 UTCGHSA enrichment
  10. 2026-09-21 19:46 UTCGHSA enrichment
  11. 2026-09-20 20:38 UTCEG score recompute
  12. 2026-09-20 20:38 UTCGHSA enrichment
  13. 2026-09-19 21:54 UTCEG score recompute
  14. 2026-09-19 21:54 UTCGHSA enrichment
  15. 2026-09-18 23:08 UTCEG score recompute
  16. 2026-09-18 23:08 UTCGHSA enrichment
  17. 2026-09-18 19:27 UTCEPSS rescore
  18. 2026-09-18 00:23 UTCEG score recompute
  19. 2026-09-18 00:23 UTCGHSA enrichment
  20. 2026-09-16 23:49 UTCEG score recompute
  21. 2026-09-16 23:49 UTCGHSA enrichment
  22. 2026-09-16 14:07 UTCEPSS rescore
  23. 2026-09-16 05:14 UTCEPSS rescore
  24. 2026-09-15 21:52 UTCEG score recompute
  25. 2026-09-15 21:51 UTCGHSA enrichment
  26. 2026-09-14 21:41 UTCGHSA enrichment
  27. 2026-09-13 22:32 UTCEG score recompute
  28. 2026-09-13 22:32 UTCGHSA enrichment
  29. 2026-09-13 16:46 UTCEPSS rescore
  30. 2026-09-12 23:48 UTCEG score recompute
  31. 2026-09-12 23:48 UTCGHSA enrichment
  32. 2026-09-12 15:00 UTCEPSS rescore
  33. 2026-09-12 01:03 UTCEG score recompute
  34. 2026-09-12 01:03 UTCGHSA enrichment
  35. 2026-09-11 14:52 UTCEPSS rescore
  36. 2026-09-11 09:36 UTCEPSS rescore
  37. 2026-09-11 02:18 UTCEG score recompute
  38. 2026-09-11 02:18 UTCGHSA enrichment
  39. 2026-09-10 09:34 UTCEPSS rescore
  40. 2026-09-10 03:34 UTCGHSA enrichment
  41. 2026-09-09 04:50 UTCEG score recompute
  42. 2026-09-09 04:50 UTCGHSA enrichment
  43. 2026-09-08 22:00 UTCEPSS rescore
  44. 2026-09-07 20:44 UTCEG score recompute
  45. 2026-09-07 20:44 UTCGHSA enrichment
  46. 2026-09-07 16:01 UTCEPSS rescore
  47. 2026-09-06 21:56 UTCEG score recompute
  48. 2026-09-06 21:56 UTCGHSA enrichment
  49. 2026-09-06 13:47 UTCEPSS rescore
  50. 2026-09-05 23:11 UTCEG score recompute
  51. 2026-09-05 23:10 UTCGHSA enrichment
  52. 2026-09-05 00:27 UTCEG score recompute
  53. 2026-09-05 00:26 UTCGHSA enrichment
  54. 2026-09-04 05:06 UTCEPSS rescore
  55. 2026-09-04 01:00 UTCGHSA enrichment
  56. 2026-09-03 00:57 UTCEG score recompute
  57. 2026-09-03 00:57 UTCGHSA enrichment
  58. 2026-09-02 14:11 UTCEPSS rescore
  59. 2026-09-02 01:59 UTCEG score recompute
  60. 2026-09-02 01:59 UTCGHSA enrichment
  61. 2026-09-01 13:53 UTCEPSS rescore
  62. 2026-09-01 04:39 UTCEPSS rescore
  63. 2026-09-01 03:14 UTCGHSA enrichment
  64. 2026-08-31 04:24 UTCEG score recompute
  65. 2026-08-31 04:24 UTCGHSA enrichment
  66. 2026-08-30 19:17 UTCEPSS rescore
  67. 2026-08-30 05:39 UTCEG score recompute
  68. 2026-08-30 05:39 UTCGHSA enrichment
  69. 2026-08-30 01:22 UTCEPSS rescore
  70. 2026-08-29 06:55 UTCEG score recompute
  71. 2026-08-29 06:55 UTCGHSA enrichment
  72. 2026-08-28 21:41 UTCEPSS rescore
  73. 2026-08-28 02:25 UTCEG score recompute
  74. 2026-08-28 02:25 UTCGHSA enrichment
  75. 2026-08-27 14:25 UTCEPSS rescore

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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 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 0.4% probability of exploitation in the next 30 days (31st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-19879?
CVE-2026-19879 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-19879?
No fix for CVE-2026-19879 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-19879 are linked in the Vendor Advisories panel on this page.

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