Long-poll NDJSON body splitting causes unbounded memory allocation in Phoenix
Allocation of Resources Without Limits or Throttling vulnerability in phoenixframework phoenix allows a denial of service via the long-poll transport's NDJSON body handling. In 'Elixir.Phoenix.Transports.LongPoll':publish/4, when a POST request is received with Content-Type: application/x-ndjson, the request body is split on newline characters using String.split/2 with no limit on the number of resulting segments. An attacker can send a body consisting entirely of newline bytes, causing a 1:1 amplification into a list of empty binaries — a 1 MB body produces approximately one million list elements, an 8 MB body approximately 8.4 million. Each element is then walked by Enum.map, materializing another list of the same size. This exhausts BEAM memory and schedulers, crashing the node and terminating all active sessions. A session token required to reach the vulnerable endpoint is freely obtainable by any client via an unauthenticated GET request to the same URL with a matching Origin header, making this attack effectively unauthenticated. This issue affects phoenix: from 1.7.0 before 1.7.22 and 1.8.6.
- Published
- May 5, 2026
- Updated
- Jun 17, 2026
- EPSS
- 0.5% · 42th percentile
- CWE
- CWE-770
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Report tools
Action score
34
Monitor
Low priority for now.
- CVSS
- 34 / 40 · 8.7 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.5%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · EEF
- 8.7
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
—
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.
phoenixframework phoenix
- 1.7.0 and later · before 1.7.22affected · semver
- 1.8.0 and later · before 1.8.6affected · semver
- 2674c6ea30634667f9b09966b90269393b445953 and lateraffected · gitfixed in 1a67c61ff9ce0a7711662ac7354861917a7c80f7, 912ea181fd247c21dbcc49fb97d0053b947d81bf
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Hex | phoenix | from 1.7.0 · before 1.7.22 | 1.7.22 |
| Hex | phoenix | from 1.8.0 · before 1.8.6 | 1.8.6 |
Same product
phoenixframework: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-56811Phoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service34Monitor
- CVE-2022-42975socket/transport.ex in Phoenix before 1.6.14 mishandles check_origin wildcarding.30Monitor
- CVE-2026-56812Phoenix JavaScript presence client crashes on presence keys colliding with Object.prototype members in Presence.syncState/syncDiff25Monitor
- CVE-2017-1000163The Phoenix Framework versions 1.0.0 through 1.0.4, 1.1.0 through 1.1.6, 1.2.0, 1.2.2 and 1.3.0-rc.0 are vulnerable to unvalidated URL redir25Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| phoenixframework phoenix | 1.7.22 | Vendor (CNA) |
| phoenixframework phoenix | 1.8.6 | Vendor (CNA) |
| phoenixframework phoenix | 1a67c61ff9ce0a7711662ac7354861917a7c80f7 | Vendor (CNA) |
| phoenixframework phoenix | 912ea181fd247c21dbcc49fb97d0053b947d81bf | Vendor (CNA) |
| Hex:phoenix | 1.7.22 | Package registry (OSV) |
| Hex:phoenix | 1.8.6 | Package 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.
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.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Peter Ullrichfinder
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-5681163 days apartPhoenix transports do not limit channel joins per connection, enabling process-exhaustion denial of service34Monitor
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
- Integrity
- Availability
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-770 · Allocation of Resources Without Limits or ThrottlingCVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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.
Attack patterns (CAPEC)
- FloodingCAPEC-125likelihood: High · Medium
- Excessive AllocationCAPEC-130likelihood: Medium · Medium
- XML Ping of the DeathCAPEC-147likelihood: Low · Medium
- Exponential Data ExpansionCAPEC-197likelihood: High · Medium
- Serialized Data Parameter BlowupCAPEC-229likelihood: High · High
- Serialized Data with Nested PayloadsCAPEC-230likelihood: Medium · High
- Oversized Serialized Data PayloadsCAPEC-231likelihood: Medium · High
- HTTP DoSCAPEC-469Low
ATT&CK techniques
- Network Denial of Service:Direct Network FloodT1498.001
- Network Denial of Service:Reflection AmplificationT1498.002
- Endpoint Denial of ServiceT1499
- Endpoint Denial of Service: OS Exhaustion FloodT1499.001
- Endpoint Denial of Service:Service Exhaustion FloodT1499.002
- Endpoint Denial of Service:Application Exhaustion FloodT1499.003
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- cna.erlef.org/cves/CVE-2026-32689.html
- github.com/phoenixframework/phoenix/commit/1a67c61ff9ce0a7711662ac7354861917a7c80f7
- github.com/phoenixframework/phoenix/commit/912ea181fd247c21dbcc49fb97d0053b947d81bf
- github.com/phoenixframework/phoenix/security/advisories/GHSA-628h-q48j-jr6q
- osv.dev/vulnerability/EEF-CVE-2026-32689
Vendor advisories and official records. Exploit/PoC links are deliberately left out.