3.7

CVE-2026-40194: phpseclib Observable Timing Discrepancy

CVSS: 3.7v3.1LowModified
AliasesUBUNTU-CVE-2026-40194DEBIAN-CVE-2026-40194CGA-89qq-r89v-24gj
Published 10-04-2026Last modified 08-05-2026
Open JSON

Vulnerability summary

CVE-2026-40194 is a low (CVSS 3.7) Observable Timing Discrepancy vulnerability in phpseclib. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.2% of scored vulnerabilities.

Overall risk
15/100
0100
Low · default modelHow is this calculated?
CVSS score
3.7/10
010
Low · v3.1 (CVE.org)
EPSS score
0.37%
0%100%
Low · +0.01 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 1 · Related 2
USN-8830-1CGA-WFCR-9XQV-QR38

Timeline

  1. 10-04-2026
    PublishedVulnerability first disclosed.
  2. 08-05-2026
    Last modifiedVulnerability information updated.

Description

phpseclib is a PHP secure communications library. Starting in 0.1.1 and prior to 3.0.51, 2.0.53, and 1.0.28, phpseclib\Net\SSH2::get_binary_packet() uses PHP's != operator to compare a received SSH packet HMAC against the locally computed HMAC. != on equal-length binary strings in PHP uses memcmp(), which short-circuits on the first differing byte. This is a real variable-time comparison (CWE-208), proven by scaling benchmarks. This vulnerability is fixed in 3.0.51, 2.0.53, and 1.0.28.

CVSS metrics

6 scores · 6 sources · 1 version

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

29%

Versus all other CVEs

30-day change

+0.01 pp

From 0.36% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.37%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard4 products
  • nextcloud-server-30All versions (No fix recorded)
  • nextcloud-server-31All versions (No fix recorded)
  • nextcloud-server-32< 32.0.8-r2
  • nextcloud-server-33< 33.0.3-r0
Debian3 products
  • php-phpseclib< 2.0.42-1+deb12u4 | < 2.0.48-3+deb13u2 | < 2.0.53-1
  • php-phpseclib3< 3.0.19-1+deb12u5 | < 3.0.43-2+deb13u2 | < 3.0.51-1
  • phpseclib< 1.0.20-1+deb12u4 | < 1.0.23-6+deb13u2
Ubuntu3 products
  • php-phpseclib< 2.0.1-1ubuntu0.1~esm1 | < 2.0.9-1ubuntu0.1~esm3 | < 2.0.23-2ubuntu0.1~esm3 | < 2.0.36-1ubuntu0.1~esm3 | < 2.0.47-1ubuntu0.1~esm1 | All versions (No fix recorded) | < 2.0.51-1ubuntu0.1~esm1
  • php-phpseclib3All versions (No fix recorded)
  • phpseclibAll versions (No fix recorded)
Wolfi2 products
  • nextcloud-server-32< 32.0.8-r2
  • nextcloud-server-33< 33.0.3-r0
Phpseclib1 product
  • phpseclib≥ 0.1.1, < 1.0.28 | ≤ 1.0.27 | ≥ 2.0.0, < 2.0.53 | ≥ 3.0.0, < 3.0.51

5 vendors · 13 products

References

11 links
Show all 11 references