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NVD / CVE Program· CNA EEF

CVE-2026-56813: Cookie attribute injection in Plug.Conn.Cookies.encode/2

LowCVSS 2.1 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 8/100)

  • 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: 0.21% (FIRST EPSS).
  • Someone with local access to the system can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: elixir-plug plug 1.16.6, 1.17.4, 1.18.5.

Low priority for now. Upgrade to elixir-plug plug 1.16.6, 1.17.4, 1.18.5 or later.

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

Improper Neutralization of Parameter/Argument Delimiters vulnerability in elixir-plug plug allows an attacker to inject or override HTTP cookie attributes. The Plug.Conn.Cookies.encode/2 function in lib/plug/conn/cookies.ex builds the Set-Cookie response header by interpolating the cookie value and its path, domain, same_site, and extra attributes directly into the header without neutralizing the ; delimiter that separates cookie attributes. An application that places attacker-controlled data into a cookie value or attribute (for example via Plug.Conn.put_resp_cookie/4 when reflecting a username or preference) lets an attacker inject a ; to append or override cookie attributes (such as Domain and Path scope, or dropping the Secure and HttpOnly flags), enabling cookie tossing and session fixation. Carriage return, line feed, and null bytes are rejected by Plug.Conn header validation, so HTTP response splitting is not possible, but attribute injection through ; is not prevented. This issue affects plug: from 0.1.0 before 1.16.6, from 1.17.0 before 1.17.4, from 1.18.0 before 1.18.5, from 1.19.1 before 1.19.5, and from 1.20.0 before 1.20.3.

Published
Jul 10, 2026
Updated
Oct 24, 2026
EPSS
0.2% · 12th percentile

Report tools

JSON

Action score

8

Monitor

Low priority for now.

CVSS
8 / 40 · 2.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
2.1
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-56813

When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

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Affected 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 (EEF). Independent of NVD's CPE analysis and usually ahead of it.

  • elixir-plug plug

    • 0.1.0 and later · before 1.16.6affected · semver
    • 1.17.0 and later · before 1.17.4affected · semver
    • 1.18.0 and later · before 1.18.5affected · semver
    • 1.19.1 and later · before 1.19.5affected · semver
    • 1.20.0 and later · before 1.20.3affected · semver
    • f26876aa67aaeb38e616638aa3efbcc2fe2906a5 and lateraffected · gitfixed in 3f00dfad4e20ba88472e315c90a25742bf178f8e, a6d1248659022749869963fd302687165ecf8c8b, 4167981747fe9ce75f374b94a28861ae950ea992, 149d9ed68fee0b4f77efd1e835ce5d785856697b, eceb8315ce9a31ef784943a95a8624ebd1bc7e06

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Hexplugfrom 0.1.0 · before 1.16.61.16.6
Hexplugfrom 1.17.0 · before 1.17.41.17.4
Hexplugfrom 1.18.0 · before 1.18.51.18.5
Hexplugfrom 1.19.1 · before 1.19.51.19.5
Hexplugfrom 1.20.0 · before 1.20.31.20.3

Same product

elixir-plug: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-54892Plug: quadratic-time decoding of nested query/body parameters enables denial of service
    34Monitor
  • CVE-2026-8468Unbounded buffer accumulation in multipart header parsing causes denial of service in plug
    32Monitor
  • CVE-2026-56814Plug: multipart :length limit is not charged for part headers, enabling unbounded temp-file creation (denial of service)
    27Monitor

Published before and after this one in the same product

  • Later →CVE-2026-105963Oct 23, 2026 · Secret key base exposed in stack trace arguments on wrong-typed Plug.Crypto arguments
    20Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
elixir-plug plug1.16.6Vendor (CNA)
elixir-plug plug1.17.4Vendor (CNA)
elixir-plug plug1.18.5Vendor (CNA)
elixir-plug plug1.19.5Vendor (CNA)
elixir-plug plug1.20.3Vendor (CNA)
elixir-plug plug149d9ed68fee0b4f77efd1e835ce5d785856697bVendor (CNA)
elixir-plug plug3f00dfad4e20ba88472e315c90a25742bf178f8eVendor (CNA)
elixir-plug plug4167981747fe9ce75f374b94a28861ae950ea992Vendor (CNA)
elixir-plug pluga6d1248659022749869963fd302687165ecf8c8bVendor (CNA)
elixir-plug plugeceb8315ce9a31ef784943a95a8624ebd1bc7e06Vendor (CNA)
Hex:plug1.16.6Package registry (OSV)
Hex:plug1.17.4Package registry (OSV)
Hex:plug1.18.5Package registry (OSV)
Hex:plug1.19.5Package registry (OSV)
Hex:plug1.20.3Package registry (OSV)

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.

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Not on record for this CVE: EPSS history · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system 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
Integrity
Availability
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-141 · Improper Neutralization of Parameter/Argument Delimiters

CVSS vector

CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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.

References

Show all references (8 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records