CVE-2026-87830: In the StAX streaming WS-SecurityPolicy validator, certain relative or unsupported XPath expressions can be co

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CRITICAL 9.1REMOTEWATCHLISTUPGRADE

CVE-2026-87830 is a critical-severity flaw (CVSS 9.1) affecting wss4j. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the StAX streaming WS-SecurityPolicy validator, certain relative or unsupported XPath expressions can be converted into paths that never match the actual XML element path. A remote SOAP peer may therefore send a required element without the expected signature or encryption. Users are recommended to upgrade to versions 4.0.2 or 3.0.6 or 2.4.4, which fix this issue.

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 88%)
CISA exploited list	No
Weakness	CWE-917
Published	2026-09-30
Last modified	2026-10-06

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-06 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-30 12:17 UTCPublished CVE record published
2026-10-06 17:26 UTCUpdated Record last modified

apache wss4j UPGRADE

Affected: < 2.4.4 · >= 3.0.0 and < 3.0.6 · >= 4.0.0 and < 4.0.2

Fixed in: 2.4.4, 3.0.6, 4.0.2

Safe to downgrade to: a release before 3.0.0

1. Check installed version

apt-cache policy wss4j || rpm -q wss4j || wss4j --version

2. UPGRADE to 2.4.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade wss4j

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade wss4j

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0 (Debian / Ubuntu)

apt-cache madison wss4j sudo apt install wss4j=<VERSION_BEFORE_3.0.0> sudo apt-mark hold wss4j

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list wss4j sudo dnf downgrade wss4j-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add wss4j

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-87830?

wss4j: upgrade to 2.4.4, 3.0.6, 4.0.2. Exact commands for each OS are on this page.

Is CVE-2026-87830 being exploited?

CVE-2026-87830 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-87830 affect?

CVE-2026-87830 affects wss4j. Severity is critical (CVSS 9.1). In the StAX streaming WS-SecurityPolicy validator, certain relative or unsupported XPath expressions can be converted into paths that never match the actual XML element path. A remote SOAP peer may therefore send a required element without

How urgent is CVE-2026-87830?

Priority 45/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2026-89238 CRITICAL 9.1 UPGRADE WSS4J EncryptedHeader child confusion could promote an attacker-controlled plaintext element as the decrypted
CVE-2026-92121 HIGH 7.5 UPGRADE In the WSS4J streaming (StAX) code, a signature reference using the WS-Security STR-Transform leaves an intern
CVE-2026-95616 HIGH 7.5 UPGRADE An integer overflow in WSS4J's DER bounds check lets an oversized allocation pass validation
CVE-2026-92899 MEDIUM 4.8 UPGRADE Apache WSS4J remembers the Nonce of each UsernameToken it accepts, so a captured token cannot be reused
CVE-2026-88920 CRITICAL 9.8 UPGRADE An authentication bypass in the DOM security processor in Apache WSS4J allows unauthenticated remote attackers

References

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