CVE-2026-77341

MEDIUMPre-NVD 5.35.3
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 5.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (38th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated
5.3EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 5.3Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

cpp-httplib is a C++ header-only HTTP/HTTPS library. In version 0.49.0, the chunked-response trailer output path writes trailer header names and values directly to the socket without validating them, allowing CRLF sequences in a trailer field to inject additional headers or split the HTTP response. Unlike every other header-writing path in the library, the trailer-writing code applies none of the field-name and field-value checks that reject carriage return and line feed, so an application that places attacker-influenced data into a chunked response trailer emits attacker-controlled CRLF onto the wire. This enables HTTP response splitting, letting an attacker forge response headers or inject a second response. This issue is fixed in version 0.50.0.

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
40
EG Risk 40/100

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 (value × EchelonGraph’s weight)
Severity53% × 45%
The EG Score, 5.3 of 10.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
38th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 27, 2026

Last Modified

September 9, 2026

Advisory Details (2)

Auto-updated Aug 27, 2026
Patch available. Sources: github, github_commit.
GitHub commit Patch Available

commit 568d434e72fc (yhirose/cpp-httplib)

Patch available: yhirose/cpp-httplib v0.50.0 (contains commit 568d434e72fc)

https://github.com/yhirose/cpp-httplib/commit/568d434e72fc51729d0ad33abffb181e5f7a453d
GitHub advisoryMentions a patch (unverified)

CRLF injection via unvalidated HTTP trailer headers in chunked response writing · Advisory · yhirose/cpp-httplib · GitHub

https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-2r2h-jc8w-w66c

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
cpp-httplib0.11.4+ds-1 ... 0.41.0+ds-3~bpo13+1 (27 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
cpp-httplib0.18.7-1 ... 0.41.0+ds-3~bpo13+1 (9 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
cpp-httplib0.18.7-1 ... 0.41.0+ds-3~bpo13+1 (8 versions)
  • every version on: no fix on record
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 53× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 2 repeat rows among the latest 84 are merged into the row they repeat.

  1. 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  2. 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  3. 2026-10-12 15:37 UTCEG score recompute
  4. 2026-10-11 19:23 UTCEG score recompute
  5. 2026-10-11 16:39 UTCEG score recompute
  6. 2026-10-11 13:58 UTCEG score recompute
  7. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  8. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  9. 2026-10-10 03:54 UTCEG score recompute
  10. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 38th percentile
  11. 2026-10-09 02:53 UTCEG score recompute
  12. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  13. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  14. 2026-10-07 09:58 UTCEG score recompute
  15. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  16. 2026-10-06 09:14 UTCEG score recompute
  17. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  18. 2026-10-05 08:30 UTCEG score recompute
  19. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  20. 2026-10-04 07:46 UTCEG score recompute
  21. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  22. 2026-10-03 07:02 UTCEG score recompute
  23. 2026-10-02 06:18 UTCEG score recompute
  24. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  25. 2026-10-01 05:30 UTCEG score recompute
Show 57 more
  1. 2026-09-30 04:23 UTCEG score recompute
  2. 2026-09-29 15:24 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  3. 2026-09-28 21:12 UTCEG score recompute
  4. 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  5. 2026-09-27 16:33 UTCEG score recompute
  6. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  7. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  8. 2026-09-26 15:49 UTCEG score recompute
  9. 2026-09-26 00:28 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  10. 2026-09-25 09:04 UTCEG score recompute
  11. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 37th percentile
  12. 2026-09-24 08:20 UTCEG score recompute
  13. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  14. 2026-09-23 07:36 UTCEG score recompute
  15. 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  16. 2026-09-22 06:51 UTCEG score recompute
  17. 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  18. 2026-09-21 06:07 UTCEG score recompute
  19. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  20. 2026-09-20 05:23 UTCEG score recompute
  21. 2026-09-19 04:38 UTCEG score recompute
  22. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  23. 2026-09-18 03:54 UTCEG score recompute
  24. 2026-09-17 03:10 UTCEG score recompute
  25. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  26. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  27. 2026-09-16 02:16 UTCEG score recompute
  28. 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  29. 2026-09-14 00:48 UTCEG score recompute
  30. 2026-09-13 00:04 UTCEG score recompute
  31. 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  32. 2026-09-11 23:20 UTCEG score recompute
  33. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  34. 2026-09-10 21:56 UTCEG score recompute
  35. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  36. 2026-09-09 04:51 UTCEG score recompute
  37. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  38. 2026-09-07 03:23 UTCEG score recompute
  39. 2026-09-06 13:48 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  40. 2026-09-06 02:39 UTCEG score recompute
  41. 2026-09-05 01:55 UTCEG score recompute
  42. 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  43. 2026-09-03 00:25 UTCEG score recompute
  44. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  45. 2026-09-01 23:36 UTCEG score recompute
  46. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  47. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  48. 2026-08-30 22:08 UTCEG score recompute
  49. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  50. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  51. 2026-08-29 21:24 UTCEG score recompute
  52. 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  53. 2026-08-28 20:40 UTCEG score recompute
  54. 2026-08-28 19:46 UTCEG score recompute
  55. 2026-08-28 00:30 UTCEG score recompute
  56. 2026-08-27 23:23 UTCEG score recomputeFirst assessed: 5.3 MEDIUM
  57. 2026-08-27 23:22 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-77341?
CVE-2026-77341 is a medium-severity vulnerability; its CVE record was published on August 27, 2026. cpp-httplib is a C++ header-only HTTP/HTTPS library. In version 0.49.0, the chunked-response trailer output path writes trailer header names and values directly to the socket without validating them, allowing CRLF sequences in a trailer field to inject additional headers or split the HTTP response.…
When was the CVE record for CVE-2026-77341 published?
The CVE record for CVE-2026-77341 was published on August 27, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 9, 2026; the record at its source may have been updated since.
Is CVE-2026-77341 actively exploited?
CVE-2026-77341 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (38th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-77341?
CVE-2026-77341 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-2026-77341?
A fix for CVE-2026-77341 is available: update to the fixed version the vendor names in its advisory.

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