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Medium

Session Fixation Escalation in Spring Framework WebFlux

IdentifiersCVE-2026-41839CWE-384· Session Fixation

CVE-2026-41839 is a low-severity session fixation-style escalation vulnerability affecting Spring Framework WebFlux applications. According to the provided content, if a WebFlux application has a compromised subdomain—such as one compromised through cross-site scripting (XSS)—an attacker can exchange a known session ID for that of an authenticated user. The issue affects Spring Framework 7.0.0 through 7.0.7, 6.2.0 through 6.2.18, 6.1.0 through 6.1.27, and 5.3.0 through 5.3.48, including unsupported versions in those ranges.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can allow an attacker to perform session fixation-based account/session escalation, resulting in unauthorized access in the context of an authenticated user. Based on the provided CVSS context, the confidentiality and integrity impacts are low, with no stated availability impact.

Mitigation

If you can’t patch tonight, do this now.

The provided content states that no further mitigation steps are necessary beyond upgrading. Until patching is completed, reduce exposure by preventing subdomain compromise, addressing XSS, verifying subdomain configuration, and limiting trust relationships between subdomains where possible.

Remediation

Patch, then assume compromise.

Upgrade Spring Framework to a fixed release for the relevant branch. The provided content identifies fixes in 7.0.8 and 6.2.19 for OSS users, with additional commercial fixes listed as 7.0.7.1, 6.2.18.1, 6.1.28, and 5.3.49 for supported branches. Spring stated that users of affected versions should upgrade to the corresponding fixed version.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
BroadcomSpring Frameworkapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

2 SOURCESView more in app
What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-41839
NVD
nvd.nist.gov/vuln/detail/CVE-2026-41839
MITRE CWE · CWE-384
Session Fixation
spring.io
spring.io/security/cve-2026-41839