CVE-2026-19879: Io.undertow/undertow: undertow: http response header integrity issue due to character truncation
Noroxi assessment
Priority: Monitor (action score 21/100)
- The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
- Probability of exploitation in the next 30 days: 0.39% (FIRST EPSS).
- Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
- According to CISA the attack is automatable: targets can be found by mass scanning.
- According to the record, no fixed version is available yet.
Low priority for now. Update when a fix is released; follow the vendor's advisory.
Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it
Primary sources: NVD · CVE.org · FIRST EPSS
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.
- Published
- Aug 14, 2026
- Updated
- Nov 5, 2026
- EPSS
- 0.3% · 33th percentile
- CWE
- CWE-681
Report tools
Action score
21
Monitor
Low priority for now.
- CVSS
- 21 / 40 · 5.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · redhat
- 5.3
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- No fixed version yet
If any of these changes, we'll tell you in the daily email digest.
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Noroxi analysis
What does it mean in your environment?
The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.
We use this product, ask for helpAffected systems
Is your version affected?
Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.
Red Hat Red Hat build of Apache Camel for Spring Boot 4
- all versionsaffected
- all versionsaffected
- all versionsaffected
- all versionsaffected
Red Hat Red Hat Enterprise Linux 10
- all versionsaffected
Red Hat Red Hat Enterprise Linux 8
- all versionsaffected
- all versionsaffected
Red Hat Red Hat Enterprise Linux 9
- all versionsaffected
Red Hat Red Hat JBoss Enterprise Application Platform 7
- all versionsaffected
- all versionsaffected
- all versionsaffected
- all versionsaffected
- all versionsaffected
- all versionsaffected
- all versionsaffected
Red Hat Red Hat JBoss Enterprise Application Platform 8
- all versionsaffected
- all versionsaffected
- all versionsaffected
Red Hat Red Hat JBoss Enterprise Application Platform Expansion Pack
- all versionsaffected
- all versionsaffected
- all versionsaffected
Red Hat Red Hat Single Sign-On 7
- all versionsaffected
- all versionsaffected
- all versionsaffected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:14 | undertow | from 0 | — |
Same product
red hat: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-93576Io.netty/netty-codec-smtp: netty netty-codec-smtp — smtp command-name field is not crlf-validated (incomplete fix of cve-2025-59419)30Monitor
- CVE-2026-93560Io.netty/netty-codec-stomp: netty: stomp codec content-length long-to-int truncation causes infinite decode loop dos30Monitor
- CVE-2026-93572Io.netty/netty-codec-redis: netty: redisarrayaggregator nested resp headers multiply patched preallocation limits30Monitor
Published before and after this one in the same product
- Later →CVE-2026-81624Aug 31, 2026 · Undertow-core: undertow: websocketcontainer defaults for buffers and timeouts are infinite30Monitor
- Later →CVE-2026-93493Sep 18, 2026 · Io.netty/netty-handler-ssl-ocsp: netty: ocsp validation silently skipped when a response omits the optional nextupdate field23Monitor
- Later →CVE-2026-93494Sep 18, 2026 · Io.netty/netty-codec-stomp: netty: bytebuf leak in stompsubframedecoder when a frame body is never terminated30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-681 · Incorrect Conversion between Numeric TypesCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
Show all references (1 more)Show less
Vendor advisories and official records. Exploit/PoC links are deliberately left out.